Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.39	11.153%	$48.2293	$48.23	$48.25	$48.20
Purchase #2	$97.44	12.347%	$109.4709	$109.47	$109.45	$109.50
Purchase #3	$209.65	13.604%	$238.1708	$238.17	$238.15	$238.20
Purchase #4	$14.83	11.362%	$16.515	$16.52	$16.50	$16.50
Purchase #5	$68.80	5.400%	$72.5152	$72.52	$72.50	$72.50
Purchase #6	$127.98	6.742%	$136.6084	$136.61	$136.60	$136.60
Purchase #7	$242.73	5.299%	$255.5923	$255.59	$255.60	$255.60
7 purchase totals =	$804.82		$877.1019	$877.11	$877.05	$877.10